Power converters mounted in electric rolling stock, under the control of a control unit, convert power supplied from a power source via an overhead contact line into power for driving a traction motor. The converted power is output to a traction motor which runs the electric rolling stock.
In order to inspect whether the control unit is operating normally, a sequence test is performed that causes the control unit to execute control while the supply of power from an overhead contact line to the power converter is shut off. Patent Literature 1 for instance, presents a sequence test circuit of an AC electric rolling stock.